The objective of this project is model how the vestibular system contributes to maintaining binocular fixation in space during motions that induce linear and angular accelerations of the head and body. We have hypothesized that the angular and linear vestibulo-ocular reflexes (aVOR and IVOR) can be characterized through the activation of compensatory and spatial orientation mechanisms. In the proposed work, we will extend these ideas by combining version and vergence to study whether binocular viewing can also be characterized in terms of the compensatory and orienting theory. A methodology for recording binocular eye movements in three dimensions using a rotating field coil system has been developed. A new mathematical methodology has been proposed to obtain the rotation of the two eyes in terms of convergence and version matrices in head coordinates. Algorithms have been proposed that will utilize these matrices and a vector from the head coordinate frame origin to each eye to compute gaze fixation points. Preliminary studies indicate monkeys can be trained to fixate targets at various positions in the visual field to calibrate each eye. In the first specific aim, monkeys will be linearly accelerated along naso-occipital and other cardinal axes at 0.5-4 Hz, while viewing targets in space at various angles and distances from the origin of the head frame. This will test the compensatory properties of the IVOR. In specific aim 2, we will utilize translation while rotating (TWR) to determine how low frequency linear acceleration affects the binocular gaze characteristics of the IVOR, which we hypothesize will be generated by the binocular orientation mechanisms that will tend to align binocular fixation with the net gravito-inertial acceleration (GIA). In specific aim 3, monkeys will be tested using linear acceleration along the axis of the gravitational acceleration. We hypothesize that this will induce compensatory oculomotor responses without the usual concomitant orientation responses at midband frequencies. We expect that compensatory response will maintain fixed gaze points in space while orientation responses will tend to align the eyes or eye velocity with the resultant GIA. We will also model the three-dimensional compensatory and orientation convergence and version interaction as described in specific aim 4. When the study is completed, we will have a quantitative model of how the vestibular system contributes to maintenance of binocular gaze stability while moving.